The use of a multi-nozzle ink jet printhead in an ink jet printer is well known in the prior art. Such a printhead has been used to print postage indicia in an electronic postage meter. Generally the nozzles of the printhead are linearly arrayed along a direction which is perpendicular to the direction of movement of the print medium relative to the printhead. Whether the nozzle array is vertical or at an oblique angle, each nozzle prints a row of dots in the course of printing the postage indicia in a postage meter.
A problem associated with the use of any multi-nozzle ink jet printhead is that it is possible for a nozzle to malfunction so that it becomes unable to eject ink in response to activation. For every nozzle that is unable to eject ink in response to activation, there will be a corresponding row on the print medium which is blank, i.e., has no dots.
This problem is particularly serious in the case of an ink jet printhead incorporated in a postage meter. It is possible that the failure to print one row of dots in the plurality of rows making up the postage indicia will render the postage indicia or some portion thereof indecipherable. In particular, it is possible that the printed postage amount will be indecipherable, causing the postal authorities to refuse to deliver the piece of mail on which the postage indicia have been printed. This is particularly true in the case of numerals which are printed with a stroke of consecutive dots in a row, such as numerals 2, 4, 5, and 7. Such defectively printed postage indicia will result in a monetary loss to the postage meter user since in the conventional secure postage meter, it is impossible to print postage indicia unless the postage amount being indicated has been accounted for within the postage meter. Since the postage meter user must account to the postal authorities for all postage printed, the meter user will also end up paying for any printed postage amount even if the postage indicia representing that amount was indecipherable, rendering the piece of mail undeliverable.